This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-219447, filed Jul. 19, 2000; and No. 2000-275890, filed Sep. 12, 2000, the entire contents of both of which are incorporated herein by reference.
The present invention relates to a magnetic recording apparatus and a magnetic recording medium used in the magnetic recording apparatus.
In recent years, a magnetic recording medium come to be required in higher recording density, particularly, the fields of the hard disc drive (HDD) and the digital voice tape recorder (DVTR) in accordance with progress in the performance of a computer, and use of the digital system and progress in the quality of the image-voice.
For example, if it is intended to achieve a high recording density by making finer the recording bits in the ordinary longitudinal recording, that the coercive force is made higher than the thermal decay of the recording magnetization and a problem that the coercive force is too high to record is generated. In order to avoid the problem, in recent years, a perpendicular magnetic recording system using a perpendicular magnetic recording layer having a perpendicular anisotropy is proposed.
In the perpendicular magnetic recording system, a perpendicular magnetic recording medium comprising a magnetic recording layer having an easy axis of magnetization in a thickness (perpendicular) direction of the magnetic recording medium. Signals can be recorded by a perpendicular magnetic recording head with a strong magnetization distribution in the thickness direction to the magnetic recording medium so as to magnetize the perpendicular magnetic recording medium in the thickness direction and to allow the magnetization to remain.
A known perpendicular magnetic recording medium includes a single layer structure in which a single perpendicular magnetic recording layer is formed on a substrate and a double layer structure in which a soft magnetic underlying layer of a high permeability and a perpendicular magnetic recording layer are formed on a substrate. As disclosed in, for example, Japanese Patent Disclosure (Kokai) No. 52-78403, it is known to the art that the mutual function between the magnetic head and the soft magnetic underlying film allows the perpendicular magnetic recording medium of the double layer structure to exhibit excellent recording characteristics, compared with the perpendicular magnetic recording medium of the single layer structure.
It is desirable for the soft magnetic underlying layer to exhibit a high permeability and a high saturated magnetic flux density. However, if the recording test is conducted by using the perpendicular magnetic recording medium of the double layer structure, a spike-like noise is observed. The spike-like noise is not observed when it comes to the perpendicular magnetic recording medium of the single layer structure consisting of the perpendicular magnetization film alone. As disclosed in Japanese Patent Publication (Kokoku) No. 3-53686, the noise is not uniformly generated within the medium. It is known to the art that the spike-like noise is generated in the portion where a domain wall is present, and is not generated in the portion where a domain wall is not present. The noise, which is called a Barkhausen noise, is derived from the phenomenon that the domain wall migration takes place irreversibly. Generation of the Barkhausen noise can be suppressed by employing the construction that permits suppressing the domain wall migration within the soft magnetic film, which is positioned below the perpendicular magnetization film, or permits completely eliminating the domain wall.
The noise generated within the magnetic recording medium also includes a white noise derived from the film characteristics of the magnetic recording medium in addition to the spike-like noise described above. In order to obtain a sufficient S/Nm, it is also necessary to improve the white noise.
A first object of the present invention is to provide a perpendicular magnetic recording medium low in noise and capable of a high density recording.
A second object of the present invention is to provide a perpendicular magnetic recording apparatus low in noise and capable of a high density recording.
According to a first aspect of the present invention, there is provided a magnetic recording medium comprising:
a nonmagnetic substrate;
a perpendicular magnetic recording layer for recording signal; and
a soft magnetic laminate layer including a soft magnetic layer which has a thickness not larger than 500 xc3x85 and a nonmagnetic layer formed between a nonmagnetic substrate and a perpendicular magnetic recording layer for recording signal.
According to a second aspect of the present invention, there is provided a magnetic recording medium comprising:
a nonmagnetic substrate;
a perpendicular magnetic recording layer;
a soft magnetic laminate layer formed between the nonmagnetic substrate and the perpendicular magnetic medium, including a first soft magnetic layer, and a second soft magnetic layer laminated on the first soft magnetic layer and differing from the first soft magnetic layer in the crystal structure.
According to a third aspect of the present invention, there is provided a magnetic recording medium comprising:
a nonmagnetic substrate;
a perpendicular magnetic recording layer;
a soft magnetic laminate layer formed between the nonmagnetic substrate and the perpendicular magnetic medium, including a soft magnetic granular layer formed of a nonmagnetic matrix and soft magnetic metal particles dispersed in the matrix, and a soft magnetic layer.
According to a fourth aspect of the present invention, there is provided a magnetic recording apparatus, comprising:
a magnetic recording medium having a nonmagnetic substrate, a soft magnetic laminate layer formed on the nonmagnetic substrate, and a perpendicular magnetic recording layer formed on the soft magnetic laminate layer;
driving means supporting and rotating the perpendicular magnetic recording medium;
a magnetic head including an element for recording information in the perpendicular magnetic recording medium and another element for reading the recorded information; and
a carriage assembly supporting the magnetic head such that the magnetic head is movable relative to the magnetic recording medium.
According to a fifth aspect of the present invention, there is provided a magnetic recording apparatus comprising:
a magnetic recording medium having a nonmagnetic substrate, a perpendicular magnetic recording layer, a soft magnetic laminate layer formed between the nonmagnetic substrate and the perpendicular magnetic medium, including a first soft magnetic layer, and a second soft magnetic layer laminated on the first soft magnetic layer and differing from the first soft magnetic layer in the crystal structure;
driving means supporting and rotating the perpendicular magnetic recording medium;
a magnetic head including an element for recording information in the perpendicular magnetic recording medium and another element for reading the recorded information; and
a carriage assembly supporting the magnetic head and making the magnetic head be movable relative to the magnetic recording medium.
According to a sixth aspect of the present invention, there is provided a magnetic recording apparatus comprising:
a magnetic recording medium having a nonmagnetic substrate, a perpendicular magnetic recording layer, a soft magnetic laminate layer formed between the nonmagnetic substrate and the perpendicular magnetic medium, including a soft magnetic granular layer formed of a nonmagnetic matrix and soft magnetic metal particles dispersed in the matrix, and a soft magnetic layer;
driving means supporting and rotating the perpendicular magnetic recording medium;
a magnetic head including an element for recording information in the perpendicular magnetic recording medium and another element for reading the recorded information; and
a carriage assembly supporting the magnetic head and making the magnetic head be movable relative to the magnetic recording medium.
According to the present invention, the soft magnetic laminate layer is used as a magnetic layer so that generation of the domain wall in the soft magnetic layer can be prevented so as to suppress the noise generation from the soft magnetic layer, thereby providing a perpendicular magnetic recording medium low in noise and capable of a high density recording.
Also, according to the present invention, the noise generation from the soft magnetic layer is suppressed by the use of the particular perpendicular magnetic recording medium so as to provide a perpendicular magnetic recording apparatus low in noise and capable of a high density recording.
Additional objects and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.